Recent reports have shed light on the dangers of prolonged sitting during long journeys, raising concerns about the risk of sudden death, particularly among certain demographics.
Last month, media outlets covered the harrowing experience of a woman who nearly lost her life due to "economy class syndrome" while traveling by train. Similarly, in February of this year, three migrant workers tragically succumbed to "economy class syndrome" while commuting long distances by bus during the Chinese New Year rush.
But what exactly is "economy class syndrome," and why does it pose a fatal threat to individuals even during seemingly routine travel by car or plane?
What is Economy Class Syndrome?
Understanding Economy Class Syndrome: Economy Class Syndrome refers to a condition known clinically as Venous Thromboembolism (VTE), which commonly manifests as Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE). In severe cases, it can lead to shock or sudden death. One of its risk factors is prolonged immobility, which increases during long-distance travel, especially in economy class flights. Hence, this phenomenon is also referred to as Economy Class Syndrome in medical terms.
Causes of Economy Class Syndrome: Economy Class Syndrome is induced by the cramped and narrow seating in transportation modes like long-distance buses, trains, and especially economy class seating on airplanes. These seats restrict movement, particularly in window seats, leading to prolonged periods of leg immobility. Extended immobility slows down venous blood flow and elevates or activates coagulation factors. Combined with other thrombotic risk factors such as endothelial injury and hypercoagulable states, this can lead to the formation of venous thrombosis.
Risks Associated with Economy Class Syndrome: If a venous thrombus forms, it may dislodge upon resuming normal activity, leading to vascular occlusion. This can result in DVT with symptoms like leg swelling, pain, increased skin temperature, and erythema. If the thrombus travels to the pulmonary artery, it can cause respiratory distress, chest pain, coughing, hemoptysis, fainting, or even sudden death. Research suggests a dose-response relationship between VTE and travel duration, with a risk increase of 18% to 26% for every additional 2 hours of flight after 4 hours. Long-distance travel by car, bus, or ship also elevates the risk of thrombosis due to prolonged sitting. However, the overall incidence of clinically symptomatic VTE post-travel is less than 0.05%, with travelers having a 2.8-fold increased risk compared to non-travelers.
Preventing Economy Class Syndrome: Current medical perspectives suggest that healthy passengers without underlying conditions or high-risk factors for VTE do not require preventive measures for Economy Class Syndrome. Although it can lead to severe consequences, the incidence of VTE post-travel is not high, and venous thrombosis typically requires the triad of blood flow alteration, endothelial injury, and blood component changes. Long-distance travel appears to only augment pre-existing VTE risk rather than causing Economy Class Syndrome in individuals with no prior risk.
Who Needs Prevention? However, individuals with VTE risk factors should consider preventive measures if their travel exceeds 4 hours. These factors include recent major surgeries, trauma, previous VTE, active malignancy, pregnancy or postpartum period, advanced age (>65 years), medication use (e.g., contraceptives, steroids, antidepressants), obesity, hereditary thrombophilia, or underlying diseases (e.g., liver, kidney, cardiovascular diseases). For passengers at particularly high VTE risk, medical evaluation may warrant pharmacological prophylaxis.
Precursors of Economy Class Syndrome:
Many DVT patients do not exhibit prodromal symptoms. However, individuals, especially those at high risk, should remain vigilant and seek medical attention promptly if experiencing symptoms during or after travel. These include leg symptoms such as swelling, pain, increased skin temperature, and erythema (typically unilateral but may be bilateral). Additionally, PE development from DVT can present progressively worsening pulmonary symptoms, potentially leading to shock or fainting within hours or minutes. Progressive pulmonary symptoms include dyspnea, progressing from exertional to resting, chest pain exacerbated by deep breathing or coughing, coughing (sometimes with hemoptysis), orthopnea, wheezing, and tachypnea. Immediate medical attention is crucial if any of these symptoms occur.
References
[1] Wang X, Wu Z. Economy class syndrome in the ED: What is the evidence? Acad Emerg Med. 2023 Feb;30(2):157. doi: 10.1111/acem.14658. Epub 2023 Jan 19. PMID: 36606707.
[2] Kenneth A Bauer. Overview of the causes of venous thrombosis. UpToDate Clinical Consultant. https://www.uptodate.com/contents/zh-Hans/overview-of-the-causes-of-venous-thrombosis. Accessed on Oct 02, 2023.
[3] Kenneth A Bauer, Menno V Huisman. Clinical presentation and diagnosis of the nonpregnant adult with suspected deep vein thrombosis of the lower extremity. UpToDate Clinical Consultant. https://www.uptodate.com/contents/zh-Hans/clinical-presentation-and-diagnosis-of-the-nonpregnant-adult-with-suspected-deep-vein-thrombosis-of-the-lower-extremity. Accessed on Oct 25, 2022.
[4] DynaMed. Pulmonary Embolism (PE). EBSCO Information Services. Accessed March 4, 2024. https://www.dynamed.com/condition/pulmonary-embolism-pe
[5] B Taylor Thompson, Christopher Kabrhel, Constantino Pena. Clinical presentation, evaluation, and diagnosis of the nonpregnant adult with suspected acute pulmonary embolism. UpToDate Clinical Consultant. https://www.uptodate.com/contents/zh-Hans/clinical-presentation-evaluation-and-diagnosis-of-the-nonpregnant-adult-with-suspected-acute-pulmonary-embolism. Accessed on Jan 19, 2024.
[6] James D Douketis, Siraj Mithoowani. Prevention of venous thromboembolism in adult travelers. UpToDate Clinical Consultant. https://www.uptodate.com/contents/zh-Hans/prevention-of-venous-thromboembolism-in-adult-travelers. Accessed on Jun 01, 2023.
Planning and Production Author: Fan Yunzhu, Attending Physician, Jia Hui Medical Reviewer: Tang Qin, Director of Science Popularization Department, Chinese Medical Association, Researcher Planning: He Tong Editor: He Tong Proofreader: Xu Lai, Lin Lin
